A variety of implanted medical devices can be used to extend and improve the life of a patient. These implanted medical devices often include electronics that monitor internal and external parameters and control the application of various therapies. To prevent body fluids from damaging electronic components that may be present within the device, the circuitry included with the internal unit is often enclosed within a hermetically sealed case. An electrical feedthrough may be used to transfer signals from the circuitry inside the hermetic case to the exterior of the case and vice versa. This electrical feedthrough maintains the integrity of the hermetic case, while allowing electrical signals to pass through.
One example of an implanted medical device is a cochlear implant. Cochlear implants include a hermetically sealed internal processor that receives and transmits electrical signals through a hermetic feedthrough. The internal processor receives electrical signals, which represent environmental sounds. The internal processor conditions these signals and selectively activates electrodes in the patient's cochlea to provide the patient with a sense of hearing. The electrical feedthrough in the hermetic housing should meet a number of rigorous requirements, including having an extremely small size, maintaining a gas and liquid seal over the patient's lifetime, mechanical reliability, providing a low electrical resistance connection between internal and external components, biocompatibility, and other requirements.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.